Accuracy And Precision In Measurement Of Radon In Water By Liquid Scintillation Counting By Uttam Saha

Uttam Saha1, Pamela Turner2, Dana Lynch3, and Derek Cooper2
1Agricultural and Environmental Services Laboratories, College of Agricultural and Environmental Sciences, The University of Georgia, Athens, GA.
2Department of Financial Planning, Housing and Consumer Economics, College of Family and Consumer Sciences, The University of Georgia, Athens, GA.
3Family and Consumer Sciences Agent, The University of Georgia Cooperative Extension, Monroe County Extension, Athens, GA.

sahau@uga.edu

Abstract

Accuracy and precision, the two important quality assurance milestones, are difficult to ascertain in measurement of radon in water because radon is a gas. This paper discusses the experience of various exercises performed in our laboratory to ascertain these two milestones. The counting efficiencies of multiple liquid radium standards purchased from a commercial vendor produced inconsistent and unacceptable counting efficiencies; thus, their use in the analysis of radon appeared questionable. Duplicate analysis of radon in 231 well water samples mostly yielded relative percentage deviation (RPD) ≤15% and seldom >15%. However, >15% RPD was mostly associated with the presence of an air bubble in one of the duplicate samples or presence of unequal sized air bubbles in both. Repeated analyses of two radon proficiency-test samples, regenerated at 40 to 60-day intervals over a period of three years, consistently yielded acceptable precision and accuracy. Thus, a proficiency testing for radon in water is a valid and valuable option and should be part of radon analysis in water.  

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